Messages in this thread | | | Date | Wed, 27 Nov 2013 13:51:09 +0200 | From | Adrian Hunter <> | Subject | Re: [PATCH] perf tools: Fix not finding kcore in buildid cache |
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On 27/11/13 13:32, Ingo Molnar wrote: > > * Adrian Hunter <adrian.hunter@intel.com> wrote: > >> On 26/11/13 18:15, Ingo Molnar wrote: >>> >>> * Adrian Hunter <adrian.hunter@intel.com> wrote: >>> >>>> The logic was not looking in the buildid cache for kcore >>>> if the host kernel buildid did not match the recorded >>>> kernel buildid. >>> >>> It would be nice to also include the specific failure mode in the >>> changelog: exactly how can users run into this. That will be more >>> useful to most people reading these changelogs than a more abstract >>> bug description. >> >> The preconditions for the problem are that kcore is in the buildid >> cache and that the running kernel has a different buildid e.g. >> >> $ perf buildid-list | grep kernel.kallsyms >> b18fbe769dea12513028a4287dae02efc1582c29 [kernel.kallsyms] >> >> $ perf record -o /tmp/junk true >/dev/null 2>&1 ; perf buildid-list -i /tmp/junk | grep kernel.kallsyms >> 504f9fd9328c40714995ce76fe1354c6e90136ce [kernel.kallsyms] >> >> >> >> Before the patch: >> >> >> $ perf script -v >out.txt >> build id event received for [kernel.kallsyms]: b18fbe769dea12513028a4287dae02efc1582c29 >> <SNIP> >> Using /home/ahunter/.debug/[kernel.kallsyms]/b18fbe769dea12513028a4287dae02efc1582c29 for symbols >> >> perf script stopped >> >> >> After the patch: >> >> >> $ perf script -v >out.txt >> build id event received for [kernel.kallsyms]: b18fbe769dea12513028a4287dae02efc1582c29 >> <SNIP> >> Using /home/ahunter/.debug/[kernel.kcore]/b18fbe769dea12513028a4287dae02efc1582c29/2013112617084061/kcore for kernel object code >> Using /home/ahunter/.debug/[kernel.kcore]/b18fbe769dea12513028a4287dae02efc1582c29/2013112617084061/kallsyms for symbols >> >> perf script stopped > > So the result of the patch is that kernel symbols get > resolved/annotated correctly, as expected from the live kcore feature, > right?
Yes but this is the non-live case i.e. the kernel has changed and we are looking at a special copy of kcore that we placed in the buildid cache (using "perf buildid-cache -v -k /proc/kcore") when the data was recorded.
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